Comparing the costs of traditional SAN versus software-defined storage

In a previous post I discussed how software-defined storage (SDS) could help IT departments to manage the increasing demand for storage capacity.

I made some bold statements that SDS will be faster, accommodate more storage space and that it's cheaper than dedicated storage hardware.

Let's do the math!

To prove that last point I will compare total cost of ownership (TCO) of a traditional HP StoreVirtual SAN solution with commodity hardware running GlusterFS.

Let's say we need three servers for our virtualisation platform. The Dell R630 is a 1U rack server which can be configured to suit our needs and will only cost us $3.500 dollar each1.

For storage, we'll go with the HP StoreVirtual 4335 (F3J70B)2 base model of 7.5TB, designed for small & medium businesses. The recommended architecture for high availability and data loss protection requires us to use a three node configuration, which will get us 22TB of raw storage3 for approx. $60.000 dollar (prices may vary). This includes 10 disks in a combination of SSD (3) and 15K SAS (7) per node.

So now we've spent $70.500 dollar on our hardware. Let's see how this compares to our software-defined storage solution.

The main benefit of SDS is that we can drop the separate dedicated storage hardware. The Dell R630 can have a chassis with 10 HDD bays so let's use those. If the goal is to buy commodity hardware, we can use consumer-grade SSD disks (just make sure to have sufficient spares). Nowadays, you can get a decent 1TB SSD for $350,-- dollar. 4

Putting an 1TB SSD in all HDD bays of three Dell servers will cost $10.500 dollar. This will give us 30TB of raw storage3 using solely SSD drives.

In total, we've spent $21.000 dollar on our SDS hardware. This gave us more storage (30TB raw storage versus 22TB) with better performance (SSD instead of 15K SAS).

That's a difference of $49.500 dollar. You can save even more if you choose regular SATA disks. It will perform less, but only costs $60,-- dollars6 per disk. With SATA disks, you can save up to $58.200 dollar compared to the SAN cluster.

The total cost of ownership

But wait, there's more to this than simply buying the hardware. We will need to start using it.

With the HP StoreVirtual SAN, the storage cluster will be up and running almost immediately. It comes with a cluster management program (HP StoreVirtual CMC) which allows us to quickly set-up our storage cluster using an intuitive GUI. It even has auto-discovery of the SAN nodes.

HP StoreVirtual CMC

With GlusterFS we'll probably first need to learn more about the principles of software-defined storage and it's architecture. Next we'll need to invest our time in getting to understand the basic commands (for instance by reading this excellent article) and implementing our storage cluster. Perhaps we'll even need some training, consultancy and support.

So we'll might end up spending most of the $49.500 dollar that we've saved from buying commodity hardware in learning how to use our new storage cluster with GlusterFS.

Does that mean that the two solutions have the same TCO?

Storage expansion & data center downsizing

No. The software-defined storage solution will be substantially cheaper due to the fact that it only requires a one-time investment to learn GlusterFS.

If we want to add more storage, the HP StoreVirtual SAN requires us to buy an additional node for roughly $20.000 dollar. With GlusterFS, we can buy commodity hardware with commodity SSD drives for $7.000 dollar. That saves us $13.000 dollar each time we need to expand our storage cluster.

We will also save costs on power usage and support fees. The annual support fee for HP StoreVirtual SAN node ranges between $1.000 and $1.500 dollar per node. Another key benefit of SDS is that it will help us reduce the complexity of our data center by removing the separate dedicated storage hardware, which will eventually reduce the TCO.

In addition, the commodity hardware can also be used to add computing power and memory to our virtualisation platform. We are not only expanding our storage, we are expanding our entire IT infrastructure.

Software-defined storage: more than a buzzword

I hope this shows that Software-defined storage is not just a buzzword, it has a strong business case as well. Especially for small business IT managers that are choosing between a traditional SAN storage system and SDS solutions.

Even if you find that GlusterFS does not fit your needs, the pricing of commercial alternatives like EMC ScaleIO and Hedvig Distributed Storage Platform will be highly competitive compared to a dedicated storage solution.

For a more thorough comparison of the commercial offerings, one should also take into account that limiting the amount of hardware will also save on power consumption, maintenance & support fees and will reduce the overall complexity of the IT infrastructure.

Once you go SDS, you'll never go back!



  3. Raw storage is the amount of disk space that is available prior to (network) RAID configuration. This is the most objective metric for comparison given that the amount of usable storage varies per system.